Wheat allergy, celiac disease and gluten sensitivity are three distinct conditions that are triggered by the ingestion of wheat gliadin (1, 2). These and all other extrinsic materials discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. In these conditions, the reaction to gluten is mediated by both cellular and humoral immune responses, resulting in the presentation of different symptomatologies. For example, in wheat allergy a specific sequence of gliadin peptides cross-links two IgE molecules on the surface of mast cells and basophils that trigger the release of mediators such as histamines and leukotrienes (3).
Celiac disease (CD) is an autoimmune condition with known genetic makeup and environmental triggers, such as gliadin peptides. CD affects between 1-2% of the general population. Throughout this application, unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints, and open-ended ranges should be interpreted to include commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.
Markers for confirming a diagnosis of this disorder are IgA against native, deamidated gliadin peptides and IgA anti-tissue trans glutaminase (tTg) autoantibody. In comparison with 10 CD, gluten sensitivity (GS) affects up to 30% of the population (4). According to two articles published in 2010 and 2011 by Sapone et al (5, 6), symptoms in GS may resemble some of the gastrointestinal symptoms that are associated with CD or wheat allergy, but it is emphasized that objective diagnostic tests for gluten sensitivity are currently missing (5, 6). While studying the innate and immune responses in CD compared to those in GS, the researchers found that TLR1, 15 TLR2 and TLR4, which are associated with innate immunity, were elevated in mucosal GS but not in CD, while biomarkers of adaptive immunity such as IFN-g, IL-21 and IL-17A were expressed in mucosal tissue in CD but not GS. They believed that measurements of toll-like receptors and IFN-y, IL-21 and IL-17A would enable them to differentiate between CD and GS (5, 6) with a method that is highly invasive and would require a biopsy. Immediate type 20 hypersensitivity to gluten is IgE mediated, while delayed type hypersensitivity to gluten is an antibody-(IgG, IgA) and T-cell-mediated reaction, which is called celiac disease or gluten sensitivity with enteropathy (7). In the absence of IgG and IgA against tTg, elevated IgG and IgA against various wheat antigens and peptides indicate the loss of mucosal immune tolerance against wheat peptides and the development of gluten sensitivity (7). Due to antigenic similarities between wheat antigens and human tissue, both CD and GS can result in many autoimmune conditions, including Type 1 diabetes, arthritis, thyroiditis, and even neuroautoimmune conditions such gluten ataxia and multiple sclerosis (8-10).
It should be appreciated that the term “patients” refer to humans under the care of a health care professional. More broadly, however, the novel testing protocols and analyses disclosed herein could be applied to non-patient humans, and any other animal that could suffer from celiac disease, gluten sensitivity, and gut-related autoimmunities.
While GS patients, similar to CD patients, are unable to tolerate gluten and can develop the same or similar sets of gastrointestinal symptoms, in GS this immune reaction does not lead to small intestine damage (5, 6). This lack of induction of intestinal damage in GS and the association of CD with genetic markers HLA DQ2/DQ8 plus small intestinal damage make the diagnosis of CD much easier than GS. The less severe clinical picture in GS, the absence of tTg autoantibodies, and the dismissal of the significance of elevated IgG and IgA autoantibodies against various wheat proteins and peptides by many clinicians makes GS an extremely dangerous disorder. This is because the persistence of IgG and/or IgA antibodies in the blood for long periods of time, along with inducers of inflammatory cascades can result in full-blown autoimmunity. If this were to be the case, due to the severity of the resulting tissue damage even implementation of a gluten-free diet might not be able to help reverse the course of the autoimmune reaction induced by IgG and IgA antibodies against different wheat antigens and peptides.
A comparison between celiac disease and gluten immune reactivity/sensitivity is shown in FIG. 1. According to this model, if two children, one with a negative genetic makeup (HLA DQ2/DQ8−), and the other with positive (HLA DQ2/DQ8+), are exposed to environmental factors, such as Rota virus, bacterial endotoxins, and some medications or their synergistic effects, the result can be a breakdown of mucosal immune tolerance in both children. The induction of mucosal immune tolerance against gliadin results in the production of IgA and/or IgG against native wheat proteins and peptides, which is the next step in the initiation of gluten sensitivity in both individuals that are HLA DQ2/DQ8− and HLA DQ2/DQ8+.
However, in the individual with the positive genetic makeup, the IgG and IgA antibodies against gliadin along with biomarkers of inflammation can activate tTg, induce damage to the villi, and result in villous atrophy. Deamidation of a specific gliadin peptide leads to the formation of a complex between it and the tTg; the presentation of this complex by antigen-presenting cells to T cells and B cells results in IgA or IgG production against tTg, deamidated gliadin and the gliadin-tTg complex. The formation of these antibodies and their detection in blood is the hallmark of CD, which is an inherited condition detected in 1-2% of the population. If CD is left untreated, the outcome could be autoimmunities and cancer.
In comparison, in an individual negative for HLA DQ2/DQ8, this breakdown in immunological tolerance and the concomitant production of IgA and or IgG against native wheat proteins and peptides may activate an inflammatory cascade. In the absence of tTg activation, however, villous atrophy does not occur. Furthermore, gliadin peptides do not go through deamidation, and consequently IgG and IgA antibodies are produced only against native wheat and gliadin peptides.
With continuous exposure to wheat antigens and continuous mucosal immune tolerance, the wheat antigens and reacting antibodies form an unholy alliance of immune complexes, resulting in severe gluten immune reactivity and sensitivity. This immune reactivity and sensitivity is a non-inherited condition detected in up to 30% of the population. If this disorder is left unchecked, prolonged exposure to IgG and IgA antibodies against wheat antigens and peptides and their cross-reaction with different tissue antigens can result in various autoimmune disorders. Therefore, even in the absence of CD, GS might still provide a productive environment for other gluten-related autoantibodies that attack different organs.
Furthermore, a gluten-free diet usually is only recommended for those who meet the criteria for a diagnosis of CD, not of gluten immune reactivity and sensitivity. Unfortunately, that leaves many gluten-sensitive people suffering unnecessarily with very serious symptoms that put them at risk for complications, conditions that might be resolved with a gluten-free diet, if they only knew.
Thus, a new paradigm is needed for aid in diagnosing and distinguishing among various gut-related diseases, including gluten immune reactivity and sensitivity, silent celiac disease, celiac disease, and gut-related autoimmunity.